Drug-Resistant HIV Spreading

1 in 4 May Be Infected With Resistant Strain

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July 8, 2002 -- A growing number of people are being infected with a form of HIV that is resistant to treatment with available medications. A new study shows one in four San Franciscans recently infected with HIV have a drug-resistant strain of the virus, which makes it more difficult to control and speeds the development of full-blown AIDS.

Researchers say the finding raises concerns about the effectiveness of HIV drugs and reveals an urgent need to develop new classes of drugs to treat people infected with the virus.

The study, which appears in the July 10 issue of The Journal of the American Medical Association, found 27.4% of newly infected patients from the San Francisco area had a form of HIV that was resistant to at least one of the three major classes of drugs used to treat HIV in 2000-2001.

Researchers say the emergence of drug-resistant HIV may be especially troublesome in areas where HIV drugs are widely used, such San Francisco, New York City, and other American or European cities.

For the study, researchers screened 225 newly infected and untreated patients from June 1996 to June 2001 and tested them for drug resistance.

The most dramatic finding was an increase in the number of people with virus resistant to a common type of HIV drug known as NNRTIs (non-nucleoside reverse transcriptase inhibitors) -- which includes Rescriptor, Sustiva, and Viramune. In 1996-97, none of the patients were resistant to these potent drugs, but by 2000-01, 13% of the patients were infected with NNRTI-resistant virus.

The number of patients infected with a strain of HIV that was resistant to another class of popular HIV drugs called protease inhibitors also increased from 2.5% in 1996-97 to 7.7% in 2000-01. These drugs include Crixivan, Fortovase, Invirase, Kaletra, Norvir, and Viracept.

The effectiveness of the two most potent classes of HIV drugs is being offset by transmission of viruses resistant to them, says researcher Robert Grant, MD, MPH, in a news release. He is assistant investigator at the Gladstone Institute of Virology and Immunology in San Francisco.

Resistance to a third class of drugs, called nucleoside reverse transcriptase inhibitors, which includes the first HIV drug AZT, decreased from 25% to 21% during the same time period.

Researchers say resistance to more than one type of drug was rare, but increased from 2.5% of patients in 1996-97 to 13% in 2000-01.

"This is an area where our data are not yet clear," says Grant. "The good news is that we found only one person out of more than 200 who was infected with a virus that was resistant to all three classes of drugs."

The study also found that drug resistance can be used to predict how long it will take for drugs to control HIV with medications. People infected with resistant strains of the virus take longer to get their viral loads under control when taking the standard combination of antiretroviral drugs.

In an editorial that accompanies the study, Joel D. Trachtenberg, MD, and Merle A. Sande, MD, of the University of Utah in Salt Lake City, say the findings highlight the need to develop new classes of drugs to treat HIV that are inexpensive and easy to produce.

"The challenges for the medical and research community are to establish strategies to treat HIV in the individual patient and to maintain potent HIV drugs as viable treatment options," they write.

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